Time base mechanism



Jan. 13, 1959 J. E. HEwITT ETAL 2,868,924

TIME BASE MECHANISM Filed June 26, 1956 United States Patent TIME BASE MECHANISM John E. Hewitt, Louis F. Schmidt, and David G. Gardner,

Lansing, Mich., assigne-rs to Abrams instrument Corporation, Lansing, Mich., a corporation of Michigan Application June' 26, 1956, Serial No. 593,987 3 Claims. (Cl. Z110-90) This invention relates to electro-mechanical devices initiating electrical pulses at an accurately controlled rate. It has particular reference to a self-contained unit utilizing its own natural period to control an impulsing mechanism, the purpose of the unit being that of a time base providing timed electrical impulses for use in an intervalometer or like device characterized by operation at repetitions timed intervals.

An object of the invention is to present a time base as described of simple compact construction and of general utility.

Another object of the invention is to provide for the production of accurately timed electrical impulses through electro-mechanical means constituting a unitary time base.

VA further object of the invention is to present a generally new construction and arrangement of parts, in a device of the kind described, for initiating the operation of, and continuing in operation, a constant period device in the form of a balance wheel and hair spring assembly.

Still another object of theinvention is to provide a spring de'tent means for the constant period device positioning it at periods of rest for operation by mechanical impulse generating means.

vOther objects and structural details of the invention will appear from the following description when read in connection with the accompanying drawings, wherein:

Fig. l is a view in side elevation, and in part diagrammatic, of a time base unit in accordance with the illustrated embodiment of the invention, the left hand mounting plate being removed;

Fig. 2 is a View of the time base unit of Fig. l in longitudinal section, some parts being omitted;

Fig. 3 is a View similar to Fig. 1, taken from the opposite side of the unit with the right hand mounting plate removed; and

Fig. 4 is a detail view showing the normally closed contacts in the unit as they appear when open.

Referring to the drawing, a time base unit in accordance with the illustrated form of the invention comprises parallel spaced apart mounting plates and 11. Supported between the plates 10 and 11 are the elements of the impulsing mechanism which operate to send timed electrical output pulses to an external place of use through out-going conductors 12 and 13. The latter are in elect continuations of in-coming power conductors 14 and 15 leading from a source of electrical current. Connected across the power conductors by means of leads 16 and 17 is an electro-magnetic device or solenoid 18. In the power conductor is an on-of control switch 19 as well as a switch 20 comprising make and break contact arms 21 andy 22, the latter switch being interposed in the line 15 between the switch 19 and the electro-magnetic device 18. In the operation of the mechanism, the switch 19 is closed so that the energizing and deenergizing of the device 18 becomes a function ofthe closing and opening movements of the contact arms 21 and 22.

The arms 21 and 22 have the form of spring blades, and, as indicated in Fig. 3, such blades are tensioned in a manner normally to engage respective contact points thereon with one another. The lower blade arm 22 extends beyond the outer end of the upper blade arm 21 and underlies a cam portion 23 on a piece 24 of a nonconductive material secured as by an eyelet to the mid area of a fork member 26. The latter is pivotally mounted on the outer end of a shaft Z7 supported between the mounting plates 10 and 11. The pivot point for the fork member 26 is in the central longitudinal plane thereof, with the cam piece 24 mounted on one side thereof. To balance or compensate for the weight of the latter, there is mounted on the fork member on the other side of the central pivot point thereof a lead slug 28.

Extending upward from its pivot point 27, the fork member 26 is formed at its upper end with an expanded portion 29 through the upper edge of which opens a V- shaped cutout 31. Adapted to enter the cut-out portion 31 is a pin 32 installed in and extending laterally from the hub of a balance wheel 33. A shaft 3d mounts the balance wheel 33 which is secured to the shaft in a concentric relation thereto. The opposite ends of the shaft 34 are received in respective bearings 3S and 36 installed in the mounting plates 11i and 11. The shaft is freely rotatable in the bearings. Near its one end, the shaft 34 is formed with a frat 37 adapted to be engaged by one end of a leaf spring 3S, the opposite end of which is anchored to a stud 39 ixed in the mounting plate 11. The leaf spring 3S, in conjunction with the flat 37, acts as a spring detent and when it is engaged with the surface 37 yieldingly holds the shaft 3d from rotation.

Near the opposite end of the shaft 341- there is attached thereto, as by a press fit, a collet 41 to which is attached one end of a hair spring 42. The opposite end of the hair spring is anchored to a stud 43 set in the mounting plate 10. The aforementioned pin 32, in the balance wheel 33, extends through and beyond the wheel on its opposite sides. The one extending end of the pin is presented for cooperation with the fork member 26 while the other extending end is presented for cooperation with an impulse arm fifi or more particularly with an upwardly extending end of such arm. The opposite end of the arm 44 is attached rto an armature member 45 pivotally connected to an ear t6 on a frame 47 forming a part of the electro-magnetic device 18. The assembly compris-- ing the arm 44 and armature is urged by a spring i8 in a clockwise direction about the ear d6 but will rock in the opposite direction upon energizing of the device 18, the armature $5 extending into cooperative relation with the coil of such device in a conventional manner.

In the operation of the unit, the parts normally assume the position shown in Figs. l to 3 under the inuence of detent spring 33, spring and the natural resilience of which maintain the contacts blade members and 22 thereon closed. The fork member 26 is at this time rocked in a leftward direction (as viewed in Fig. 3), causing the cam 23 to assume a position permitting the Contact blade arms 21 and 22 to close. Accordingly, should the on-cff switch 19 now be closed current will be supplied the out-put conductors 12 and 13, and also be supplied to the electro-magnetic device 18. The latter being thus energized, draws the armature to it and so rocks the impulse arm 4d in a leftward or coanterclockwise direction as viewed in Fig. 3. ln the course of such movement, the upper or outer end of the arm engages the pin 32, which may be termed the impulse pin, and, as such motion is continued, rocks the balance wheel 33 a short distance in a clockwise direction. rl`he arm 44 moves on and beyond the path of motion of the pin 32, as it completes its rocking motion in response to the energizing of the device 18, the arm assuming at the end of such travel substantially the position shown in dotted lines in Fig. 3. The rotary impulse given the balance wheel 33 is effective through the shaft 34 to wind the hair spring 42 or to store energy therein. As the impulse arm 44 passes out of cooperative relation with the pin aeeaaaa 32, the stored energy is released to effect an opposite or countercloclwise motion of the balance wheel. In the course of this latter motion, the impulse pin 32 enters the cut-out portion 31 of the forli member 26 and engages the right hand edge thereof (Fig. 3) in a manner to rock the forli member in a clockwise direction about its pivot This motion is eective through the cam 23 to depress the lower switch contact arm 22 out of engagement with 'the upper switch Contact arm 21, as indicated in Fig. 4, whereupon the supply of current to the out-put conductors ft2 and i3 and to electro-magnetic device 18 is interrupted. Upon the deenergizing of the device 18, the impulse arm is allowed to return to its initial position by the action of spring 48.

Referring again to the balance wheel 33, which continues its counterclockwise movement (Fig. 3) under the urging of the hair spring 42, the wheel gradually reaches a condition of equilibrium and the hair spring will start to wind up and cause the balance wheel to move in an opposite or clockwise direction. ln the course of this movement, the fork member 26 is re-engaged by the impulse pin 32 and rocked in the opposite direction back toward its starting position. The cam 23, in response thereto, rises to permit the re-engagement of spring contact arm 22 with arm 21 and a consequent reclosing of the electrical circuit from in-put conductors M and to out-put conductors 112 and 1l?) to the electromagnetic device The latter again actuates the armature 45 and impulse arm 44, which latter moves to reengage the pin and to impart another kick or impulse thereto in a counterclockwise direction for repeated, continued operation of the balance wheel and hair spring assembly. At the time of actuation of the arm 44, the balance wheel will still be moving. 1t is accordingly necessary to time the contact assembly so that the irnpulse arm will be able to overtake the impulse pin before the hair spring has caused the impulse pin to move beyond the reach of the impulse arm. Such timing permits the impulse arm to impart energy to the hair spring on each clockwise rotation of the balance wheel. in this connection, it will be understood that the leaf spring 38 and the flat surface 37 on the shaft cooperate to define for the balance wheel a normal position in which the impulse pin 32 is always presented for actuation by the impulse arm at the start of a series of operations. As long as power is applied to the unit the oscillatory motion of the balance wheel, which tog-ether with its associated parts may be considered a constant period device, will continue. The repeated opening and closing of the Contact arms 21 and 22 thus aiso occurs at regular accurately determined intervals with a consequent supply of electrical impulses to the out-put conductors of constant frequency and duration.

Beneath the pivot point 2'?, the fork member 26 is formed as a yoke in embracing relation to a sleeve 51 on a shaft 52 extending between and supported by the mounting plates il@ and 11. The shaft 52 and collar 51 thereon may be termed a banking shaft assembly which limits and donnes the alternate extremes of movement of the fork member.

What is claimed is:

1. A time base mechanism, including parallel spaced apart mounting plates, a shaft journaled between said plates, a balance wheel secured to said shaft, a hair spring anchored to one of said plates at its one end and connected to said shaft at its other end, an impulse pin on said balance wheel, an impulse arm movable to and fro between said plates and engageable with said pin to turn said wheel and store energy in said spring, said spring releasing its energy to effect an oscillating motion of said shaft and wheel, means for moving said arm in a timed relation to the movement of said balance wheel in such wise as to engage said arm with said pin at a predetermined point in the movement of said wheel in lil each cycle of oscillation thereof for the storing of additional energy in said spring, and spring detent means between said mounting plates and said balance wheel effective substantially at said point in the movement of said wheel, said spring detent means comprising a leaf spring anchored in one of said mounting plates and a flat on said shaft engageable by said leaf spring.

2. A time base mechanism, including parallel spaced apart mounting plates, a shaft journaled between said plates, a balance wheel secured to said shaft, a hair spring connected to said shaft and anchored to one of said plates, an impulse pin on said balance wheel, an impulse arm supported between said plates for pivotal movement, said arm being arranged to give an oscillatory impulse to said balance wheel through engagement with said pin, said hair spring absorbing the energy of said impulse and releasing such energy to said balance wheel for an oscillation thereof wherein said pin is repositioned to receive another impulse from said arm on a succeeding movement of said arm, electric-magnetic means supported between said plates and operative in response to the energizing and deenergizing thereof to effect a to and fro motion of said arm, and means for energizing and deenergizing said electro-magnetic means in a timed relation to the oscillation of said balance wheel, said last named means including a fork member supported between said plates for pivotal movement, an operative connection between said balance wheel and said fork member for rocking said fork member to and fro in response to the oscillations of said wheel, a pair of normally closed contacts in a timed out-put pulsing circuit further including said electro magnetic means, and a cam on said fork member opening said contacts and controlling the re-closing thereof in response to the rocking motion of said fork member.

3. A time base mechanism, including parallel spaced apart mounting plates, a shaft journaled between said plates, a balance wheel secured to said shaft, a hair spring connected to said shaft and anchored to one of said plates, an impulse pin on said balance wheel, an impulse arm supported between said plates for pivotal movement, said arm extending into parallel adjacent relation to said wheel on one side thereof and being arranged to give an oscillatory impulse to said balance wheel through engagement with said pin, said hair spring absorbing the energy of said impulse and releasing such energy to said balance wheel for an oscillation thereof wherein said pin is re-positioned to receive another impulse from said arm on a succeeding movement of said arm, electro magnetic means supported between said plates and operative in response to the energizing and de-energizing thereof to effect a to and fro motion of said arm, a fork member supported between said plates for pivotal movement and extending into parallel adjacent relation to said balance wheel on the other side thereof, pin means on said balance wheel engageable with said fork member to rock said member to and fro in response to the oscillations of said wheel, a pair of normally closed contacts in a timed out-put pulsing circuit further including said electro magnetic means, and a cam on said fork member opening said contacts and controlling the re-closing thereof in response to the rocking motion of said fork member.

References Cited in the file of this patent UNITED STATES PATENTS 

